High Level Resistance of Enterococcus faecium and E. faecalis Isolates from Municipal Sewage Treatment Plants to Gentamicin

Background: enterococci are members of the normal gut flora and released into the environment via sewage outlets,where they can survive for long times. infections with high-level gentamicin resistant (hlgr) enterococci are emergingworldwide. hlgr enterococci have developed a resistance to most antibiotics commonly used for enterococcal infectionstherefore; treatment of infections caused by hlgr enterococci is difficult. the present study investigated thedistribution and antibiotic resistance of hlgr enterococcus faecium and e. faecalis isolates from raw wastewater samplesin tehran.methods: raw wastewater samples were collected during the period from november 2006 to may 2007 at 3 sewagetreatment plants located in different parts of tehran. all 90 hlgr enterococcal isolates were identified to the specieslevel by biochemical and pcr assays and subjected to antibiotic susceptibility testing.results: sixty four percent (58 of 90) of isolates were e. faecium and 29%(26 of 90) of them were e. faecalis. thehighest level of antibiotic resistance was observed with erythromycin (63%), co-trimoxazole (69%) and tetracycline(92%) for e.faecalis and with erythromycin (97%), ciprofloxacin (47%), co-trimoxazole (45.5%) and tetracycline(47%) for e. faecium. multiresistance against 3 to 4 antimicrobial was present in 27.5% and 15.5% of the isolates, respectively.conclusion: hlgr e. faecium were more commonly found than e. faecalis. species identification of hlgr enterococcienables us to assess species-specific antibiotic susceptibility patterns in our area. the present study reviled thathlgr e. faecalis remained more susceptible than e. faecium against the usual first-line and alternative treatments.